Examples of applications for titanium alloys are such where light weight in combination with high strength is needed. Furthermore, titanium alloys are generally corrosion resistant and have good high temperature properties. Examples of applications are found in the aerospace-, chemical-, and automotive industries, in the field of sports and leisure, and in the medical field.
The most widely used titanium alloy overall is Ti-6Al-4V. It is an alpha+beta alloy which has a good balance of mechanical properties.
Titanium and titanium alloys are since a long time being used in medical devices such as implants for the human body. Such implants are, for example, hip joint prostheses, knee joint prostheses, spinal implants, bone plate systems, intramedullary nails, dental implants, cardiovascular implants, ear-implants, and nose-implants. Pure titanium is at present to a great extent used and has excellent biocompatibility but has drawbacks in some applications due to its mechanical properties such as strength. The alloy Ti-6Al-4V has good mechanical properties such as high strength, and has also excellent biocompatibility. It has therefore been used as an alternative to pure titanium. However, there is a growing concern about the risks of exposing the human body to aluminium and vanadium. It would therefore be desirable to find alternative alloys not containing these elements, while still having excellent, or even improved, mechanical properties, and excellent biocompatibility. Such an alloy would also find use in non-medical applications as an alternative to Ti-6Al-4V.
There is a need for titanium-based alloys which are not based on aluminium and/or vanadium, especially useful for medical implants, and which especially have mechanical properties, such as hardness, on the same level as, or better than, Ti-6Al-4V.
EP 0 707 085 A1 discloses a biocompatible alloy of Ti containing 2.5-13 wt % Zr, 20-40 wt % Nb and 4.5-25 wt % Ta. The ratio of Nb/Ta is between 2 and 13. Preferred alloys are Ti-12.4Ta-29.2Nb-7.1Zr, Ti-21.6Ta-23.8Nb-4.6Zr, and Ti-5.7Ta-35.3Nb-7.3Zr.
U.S. Pat. No. 5,169,597 discloses a biocompatible titanium alloy containing either 10-20 wt % Nb or 35-50 wt % Nb, and 13-20 wt % Zr.
EP 0 640 353 A1 discloses a surface and near surface hardened implant of titanium alloys comprising a core of a titanium alloy containing either 10-20 wt % Nb or 35-50 wt % Nb, and 0.5-20 wt % Zr.
U.S. Pat. No. 5,415,704 discloses an alloy of Ti—Nb—Zr with less than 2 wt % of a solute of, e.g., Ta.
Kuroda et al., “Design and mechanical properties of new beta type titanium alloys for implant materials”, Materials Science and Engineering A243, 244-249, 1998, discloses an alloy Ti-13Ta-29Nb-4.6Zr.
Many of the prior art alloys containing titanium for implant purposes contain comparatively low atomic percentage of titanium.